After only one season on American Idol, Ellen DeGeneres has announced she is leaving her judging job on the Fox reality show because the role wasn’t the “right fit” for her. “Dim the lights… I’ve voted myself off American Idol,” the talk-show host wrote on Twitter last night. DeGeneres was recruited to fill the gap left by Paula Abdul, who didn’t renew her contract after Season Eight. DeGeneres’ announcement, along with the departure of founding judge Simon Cowell, leaves producers with the task of revamping and revitalizing the slumping show’s talent lineup before the start of Season 10.

An industry source told People that Jennifer Lopez — who has performed on Idol and served as a guest mentor — will step in to replace Ellen as a judge. Both TMZ and Gossip Cop are reporting that Idol producers have also extended an offer to Aerosmith’s Steven Tyler to join the show as a judge and current judge Kara DioGuardi is being forced off the show. Fox would not comment on the reports, but an announcement regarding the show’s Season 10 roster is expected to be made next Monday, August 2nd, at Fox’s annual Television Critics Tour.

“A couple months ago, I let Fox and the American Idol producers know that this didn’t feel like the right fit for me,” DeGeneres said in a statement, adding that her busy schedule became “more than I bargained for.” She reportedly had signed a five-year, multi-million-dollar contract for the Idol gig in addition to her day job as host of The Ellen DeGeneres Show. “I also realized this season that while I love discovering, supporting and nurturing young talent, it was hard for me to judge people and sometimes hurt their feelings.” DeGeneres, who has no musical background, came under fire last season for her fluffy critiques that rarely included sharp analysis of the singers’ vocal performances. She also reportedly clashed with the show’s harshest critic, Cowell, behind the scenes. “As I got to know Ellen, I grew to really, really like her,” Cowell told the Hollywood Reporter last night. “I have huge respect for her because she’s always been in control of her own destiny.” Host Ryan Seacrest tweeted, “I will miss her on ‘Idol.’ She’s one of the kindest and most talented people in Hollywood!”

As Rolling Stone previously reported, Nigel Lythgoe, one of Idol‘s original producers, is expected to return to the show for its tenth season (he left to start up and judge So You Think You Can Dance). Should Lythgoe take over the show, he’s promised to restock the judges’ table and return to a three-judge format. DioGuardi joined the show for Season Eight, when the show expanded to include four judges. Viewers have said they find the extra critique superfluous and time-consuming, and while DioGuardi wasn’t a fan favorite on her debut season, she settled in to her new job during Season Nine.

Chris Isaak, Harry Connick, Jr., and Jessica Simpson are all rumored to be in the running to replace Cowell on American Idol, which suffered a dip in ratings for the first time this past season. Reps for Justin Timberlake and Elton John have denied their clients are considering the judge’s job; previously, personalities as diverse as Howard Stern and Perez Hilton were floated as possible Cowell replacements. Idol will face additional competition from Cowell’s own American version of The X Factor, which debuts in the fall of 2011.